Existing mobile device data storage systems tend to secure and store files in a way that is inefficient. For example, many mobile device data storage systems secure files by directly encrypting the entire file. In this case, the entire file is decrypted and/or re-encrypted upon each file access. Directly encrypting and/or decrypting an entire file may require significant processing overhead thereby reducing storage system performance, especially when a file is large. In addition, many existing techniques used to verify the integrity and/or authenticity of a file may be circumvented in certain situations, especially in the case of mobile devices. It would be useful if a scheme for securely storing file data could be developed that would reduce processing overhead and/or allow for reliable determination of file integrity.